Crystallized glass

ABSTRACT

To provide a crystallized glass capable of attaining the same clarification effect as in the composition containing an arsenic component and an antimony component even in the case of having the composition containing no arsenic component, while maintaining various physical properties peculiar to a Li 2 O—Al 2 O 3 —SiO 2 -based crystallized glass. Disclosed is a crystallized glass which is characterized by containing a predetermined amount of Li 2 O, Al 2 O 3 , and SiO 2  components (on an oxide basis), and containing a predetermined amount of BaO component (on an oxide basis) and the like. This crystallized glass preferably contains β-quartz and/or β-quartz solid solution as main crystal phase(s), an average crystal particle size of the main crystal phase(s) being preferably within a range between 5 and 200 nm.

This application is based on and claims the benefit of priority fromJapanese Patent Application Nos. 2013-226567 and 2014-195401,respectively filed on 31 Oct. 2013 and 25 Sep. 2014, the contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Li₂O—Al₂O—SiO₂-based crystallizedglass.

2. Related Art

A Li₂O—Al₂O₃—SiO₂-based crystallized glass containing 3-quartz and/orβ-quartz solid solution has a low average expansion coefficient, anduseful physical properties intrinsic to a crystallized glass based onthis system, such as high rigidity and ultra-surface-smoothness afterpolishing. Because of these characteristics, there have been made astudy of use of the crystallized glass based on this system as a mirrorsubstrate material and a photomask substrate material of anext-generation semiconductor production device in which extremeultraviolet lithography (EUVL) technology using extreme ultraviolet raysas a light source is employed. The crystallized glass required for theseapplications has been required to contain fewer remaining bubbles, whichexert an influence on a surface shape, so as to haveultra-surface-smoothness.

Meanwhile, in the Li₂O—Al₂O₃—SiO₂-based crystallized glass, a precursorglass commonly has a high melting temperature of 1,450 to 1,600° C. inthe production process thereof. In this crystallized glass, a clarifyingagent has been added for the purpose of homogenizing and clarifying theglass melt during melting of the production process, and an arseniccomponent has frequently been used as the clarifying agent having theeffect within the above-mentioned high temperature range. However, thearsenic component may exert an adverse influence on the human body andenvironment, and requirements of refraining from use of these componentsas much as possible have become higher and higher.

-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. 2011-173748-   Patent Document 2: Japanese Unexamined Patent Application,    Publication No. 2011-201763-   Patent Documents 1 and 2 mentioned above disclose    Li₂O—Al₂O₃—SiO₂-based crystallized glasses, and suggest some    clarifying agents other than an As₂O₃ component and an Sb₂O₃    component.

In Patent Document 1, the clarification effect is exerted by inclusionof rare earth oxide and halogen when a Li₂O—Al₂O₃—SiO₂-based glassmaterial is melted. However, halogen such as Cl and a compoundcontaining halogen used in a glass material in Patent Document 1 aretoxic, and apply a large burden on the human body and productionfacilities. The rare earth oxide used in Patent Document 1 isdisadvantageous in view of stable supply and cost.

In Patent Document 2, the clarification effect is exerted by inclusionof SnO₂ and additional clarifying agents such as Sb₂O₃, Cl⁻, Br⁻, andSO₄ ²⁻ when a Li₂O—Al₂O₃—SiO₂-based glass material is melted. However,in a crystallized glass of Patent Document 2, SnO₂ is used as theclarifying agent and there is a problem that desired physical propertiescannot be obtained by devitrification of the crystallized glass. Amongadditional clarifying agents in Patent Document 2, Cl and Br, and acompound containing Cl and Br are toxic and apply a large burden on thehuman body and production facilities. In Patent Document 2, Sb₂O₃, whichis a component capable of becoming environmentally harmful, is used asadditional clarifying agents, thus being disadvantageous in view of anenvironmental burden.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a crystallized glasscapable of attaining the same clarification effect as in the compositioncontaining an arsenic component and an antimony component even in thecase of having the composition free from a component which exerts anadverse influence on the human body and environment such as an arseniccomponent, while maintaining various physical properties peculiar to aLi₂O—Al₂O₃—SiO₂-based crystallized glass.

The present inventors have intensively studied so as to attain theobject mentioned above and, as a result, the present invention has beencompleted by inclusion of a BaO component in a crystallized glasscontaining the respective components such as SiO₂, Al₂O₃, and Li₂O, andpreferably controlling the content of these components within a specificrange. Thus, preferred embodiments of the invention can be representedby the following constitutions.

(Constitution 1)

A crystallized glass which does not substantially contain As₂O₃component (on an oxide basis) as a clarifying agent, including, in termsof percent by mass on an oxide basis:

an SiO₂ component between 30 and 70%,

an Al₂O₃ component between 10 and 40%,

a Li₂O component between 0 and 10% (excluding 0%),

a P₂O₅ component between 5 and 15%,

a ZnO component between 0 and 5.5%, and

a BaO component between 0 and 5% (excluding 0%),

wherein the total content of the BaO component and the ZnO component (onan oxide basis) is 1% by mass or more.

(Constitution 2)

The crystallized glass according to the constitution 1, containingβ-quartz and β-quartz solid solution as main crystal phase(s).

(Constitution 3)

The crystallized glass according to the constitution 1 or 2, wherein themain crystal phase has an average crystal particle size within a rangebetween 5 and 200 nm.

(Constitution 4)

The crystallized glass according to any one of the constitutions 1 to 3,wherein an average linear thermal expansion coefficient within atemperature range between 0 and 50° C. is within a range of0.0±1.0×10⁻⁶/° C.

(Constitution 5)

The crystallized glass according to any one of the constitutions 1 to 4,including, in terms of percent by mass on an oxide basis, a TiO₂component between 1 and 10% and/or a ZrO₂ component between 1 and 10.

(Constitution 6)

The crystallized glass according to any one of the constitutions 1 to 5,including, in terms of percent by mass on an oxide basis, an MgOcomponent between 0 and 5%, and a CaO component between 0 and 5%.

(Constitution 7)

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to any one of theconstitutions 1 to 6, including, in terms of percent by mass on an oxidebasis, an MgO component between 0 and 5%, a CaO component between 0 and5%, and a P₂O₅ component between 5 and 15%.

(Constitution 8)

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to any one of theconstitutions 1 to 7, wherein, in terms of percent by mass on an oxidebasis, a ratio of the content of the P₂O₅ component to that of the SiO₂component is 0.02 to 0.200, and a ratio of the content of the P₂O₅component to that of the Al₂O₃ component is 0.059 to 0.448.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass of the present invention iscapable of attaining the same clarification effect as in the compositioncontaining an arsenic component and an antimony component even in thecase of having the composition free from a component which exerts anadverse influence on the human body and environment such as an arseniccomponent, and maintaining various physical properties peculiar to acrystallized glass of this system.

According to a preferred embodiment of the present invention, it is alsopossible to obtain a Li₂O—Al₂O₃—SiO₂-based crystallized glass in whichthe average linear thermal expansion coefficient within a temperaturerange between 0 and 50° C. is within a range of 0.0±1.0×10⁻⁶/° C.

According to a preferred embodiment of the present invention, it is alsopossible to obtain a crystallized glass which includes fine crystalparticles having an average crystal particle size within a range between5 and 200 nm, and which is also free from ion diffusion of PbO, Na₂O,and K₂O components.

DETAILED DESCRIPTION OF THE INVENTION

One characteristic feature of the Li₂O—Al₂O₃—SiO₂-based crystallizedglass is its low expansion property. This low expansion property can beobtained by imparting a specific composition to theLi₂O—Al₂O₃—SiO₂-based crystallized glass. The constitutive members usedin the next-generation lithography technology in the production of asemiconductor by use of EUV light are required to have thermaldimensional stability, strength, thermal durability, and chemicalstability, especially ultra-low expansion characteristics which arenecessary for the thermal expansion stability. There is also made astudy of use of such Li₂O—Al₂O₃—SiO₂-based crystallized glass havingultra-low expansion characteristics in the constitutive members.

In preferred embodiment, surface polishing of the Li₂O—Al₂O₃—SiO₂-basedcrystallized glass enables a smooth surface applicable to thenext-generation lithography, which is also a characteristic feature ofthe crystallized glass.

Preferred embodiment of the crystallized glass of the present inventionwill be described below.

The “crystallized glass” as used herein means a material obtained bysubjecting a glass to a heat treatment to precipitate a crystal in theglass phase, the material comprising an amorphous solid and a crystal.

The “(maximum value−minimum value) of ΔL/L” as used herein means adifference between a maximum value and a minimum value of ΔL/L, in whichL means the length of a crystallized glass at 0° C., and ΔL means achange in length of the glass ceramics at any temperature, within anytemperature range.

The “low expansion characteristics” as used herein mean that, within thetemperature range between 0 and 50° C., the average linear thermalexpansion coefficient (α) is within a range of 0.0±1.0 (10⁻⁶/° C.) andthe (maximum value−minimum value) of ΔL/L is within a range of 10×10⁻⁶;preferably, the average linear thermal expansion coefficient is within arange of 0.0±0.2 (10⁻⁶/° C.) and the (maximum value−minimum value) ofΔL/L is 10×10⁻⁷ or less; and more preferably, the average linear thermalexpansion coefficient is within a range of 0.0±0.1 (10′/° C.) and the(maximum value-minimum value) of ΔL/L is 8×10⁻⁷ or less. As used herein,the fact that the average linear thermal expansion coefficient is thevalue within a range of 0.0±0.1 (10⁻¹⁶/° C.) refers to “ultra-lowexpansion characteristics”.

The average linear thermal expansion coefficient (α) of the crystallizedglass of the present invention is within a range of 0.0±1.0 (10⁻⁶/° C.)within the temperature range between 0 and 50° C. The materials in thefield of various semiconductor production devices and ultra-precisionmembers are required to have thermal expansion characteristics capableof coping with higher accuracy. In order to satisfy the requirements,the average linear thermal expansion coefficient within the temperaturerange between 0 and 50° C. is controlled to fall within a range of0.0±1.0 (10⁻⁷/° C.), preferably 0.0±0.5 (10⁻⁷/° C.), and still morepreferably 0.0±0.1 (10⁻⁷/° C.). The composition of the constitutivecomponents of the crystallized glass having a relation to physicalproperties is controlled to fall within the range mentioned below,whereby, the glass may easily have the physical property value a withina range of 0.0±0.5 (10⁻⁷/° C.); and when the composition is morecontrolled, the glass may be more easily have the physical propertyvalue a within a range of 0.0±0.1 (10⁻⁷/° C.).

Unless otherwise specified, the average linear thermal expansioncoefficient as used herein is expressed as a unit of (/° C.).

Similarly, in order to satisfy high expansion characteristics of thematerial capable of coping with higher accuracy required, the (maximumvalue-minimum value) of ΔL/L within a temperature range between 0 and50° C. is preferably controlled to fall within a range of 10×10⁻⁷ orless. In a preferred embodiment of the crystallized glass of the presentinvention, the (maximum value−minimum value) of ΔL/L is controlled to10×10⁻⁷ or less. More preferably, the (maximum value−minimum value) ofΔL/L is controlled to 9×10⁻⁷ or less. The crystallized glass of thepresent invention may easily obtain physical properties of (maximumvalue−minimum value) of ΔL/L of 10×10⁻⁷ or less by controllingcrystallization heat treatment conditions. It is also possible to easilyobtain physical properties of (maximum value−minimum value) of ΔL/L of9×10⁻⁷ or less by strictly controlling crystallization heat treatmentconditions, and to obtain physical properties of 8×10⁻⁷ or less.

As used herein, the main crystal phase means all the crystal phaseshaving a relatively large precipitation ratio. In other words, in anX-ray chart of X-ray diffractometry (wherein the vertical axis indicatesthe X-ray diffraction intensity, and the horizontal axis indicates thediffraction angle), when a ratio of the X-ray diffraction intensity atthe main peak of a precipitation phase (the highest peak of the crystalphase) to the X-ray diffraction intensity at the main peak (the highestpeak) of the crystal phase having the largest precipitation proportion,set at 100, is at least 30 (the ratio is hereinafter referred to as anX-ray intensity ratio), then all the crystal phases satisfying this arethe main crystal phases. The X-ray intensity ratio of the crystal phasesother than the main crystal phase is less than 20, more preferably lessthan 10, and most preferably less than 5.

Next, the surface roughness and precipitated crystal size afterpolishing will be mentioned below. In the field of various semiconductorproduction devices and ultra-precision members, the smoothness of thesubstrate surface capable of coping with higher accuracy is important.In order to maintain the smoothness, a relation between the averagecrystal particle size and the surface roughness should be noted. As usedherein, the “average crystal particle size” is an average of the crystalparticle size determined by visually measuring from a transmissionelectron micrograph. The number of measured values of the crystalparticle size to be used for calculation of the average is 30 or more.The crystal particle size is obtained by visually measuring the longestdistance between two parallel lines which sandwich the crystal particle.

When the application of the crystallized glass of the present inventionto the field of various semiconductor production devices andultra-precision members is taken into consideration, the surfaceroughness Ra after polishing of the glass is preferably 3 Å or less, andmore preferably 2 Å or less. In order to easily obtain the smoothness,the average crystal particle size of the precipitated crystal of thematerial is preferably 200 nm or less, more preferably 90 nm or less,and most preferably 80 nm or less. Meanwhile, in order to make themechanical strength of the crystallized glass fall within a desiredrange, the average crystal particle size is preferably 5 nm or more,more preferably 50 nm or more, and most preferably 60 nm or more. Itbecomes easy to obtain the value of the surface roughness Ra afterpolishing and the average crystal particle size, each falling within therange mentioned above by controlling the composition of the constitutivecomponents of the crystallized glass having a relation to theprecipitated crystal size to fall within a range mentioned below, andcontrolling the crystallization conditions.

The crystallized glass of the invention may obtain the intendedlow-expansion characteristics by precipitating the main crystal phasehaving a negative average linear thermal expansion coefficient, thusmaking the positive expansion coefficient of the glass phase offset thenegative expansion coefficient of the crystal phase. In order to obtainultra-low expansion characteristics, it is preferred to contain, as themain crystal phase of the crystallized glass, β-quartz (β-SiO₂) and/orβ-quartz solid solution (β-SiO₂ solid solution. It becomes easy toobtain ultra-low expansion characteristics by controlling thecomposition of the constitutive components of the crystallized glasshaving a relation to the precipitated crystal phase to fall within therange mentioned below, and controlling the crystallization conditions.As used herein, the β-quartz solid solution means an interstitial onewith elements other than Si and O and intercalated into β-quartz and/ora substitutional one with the elements substituted therein. Particularlypreferred is a crystalline body having Al³⁺ as substituted for Si⁴⁺ andhaving Li⁺, Mg²⁺, and Zn²⁺ added thereto for the equivalence thereof.(One typical example is β-eucryptite.)

Next, components included in the crystallized glass of the presentinvention are mentioned. Unless otherwise specified, each component is acomponent expressed on an oxide basis, and the content of each componentis expressed in terms of % by mass on an oxide basis.

As used herein, “on an oxide basis” means a method of expressing theconstitutive component in the crystallized glass of the presentinvention, when components to be used as the constitutive components ofthe crystallized glass of the present invention are presumed to be alldecomposed into their oxides during the step of melting the glassmaterial. Regarding its content, each constitutive component of thecrystallized glass is expressed in terms of percent by mass on an oxidebasis relative to the total weight of the expressed oxides, 100% bymass, in the crystallized glass.

As mentioned above, the Li₂O—Al₂O₃—SiO₂-based crystallized glasscontaining a SiO₂ component, an Al₂O₃ component, and a Li₂O component ofthe present invention is capable of attaining the same highclarification effect as in the composition containing an As₂O₃ componentby inclusion of a BaO component, while maintaining the above-mentionedcharacteristic feature.

The BaO component basically remains in the glass matrix other than thecrystals precipitated in the glass, thereby exerting some influences onthe effect of improving the ultra-low-expansion characteristics and themeltability of the glass, and exerting the clarification effect; and isan essential component for delicate control of the relative amount ofthe crystal phase and the glass matrix phase.

When the content of the BaO component is 0% or more (excluding 0%) and5% or less, low expansion characteristics are remarkably improved, andit is possible to easily obtain ultra-low expansion characteristics andto obtain high clarification effect. In addition, devitrificationresistance of the glass material is more improved and coarsening of theprecipitated crystal in the crystallized glass after the crystallizationstage due to deterioration of the devitrification resistance issuppressed, thus increasing mechanical strength.

In order to more easily obtain the effect, the lower limit of thecontent is preferably 0.3% or less, more preferably 0.5%, still morepreferably 0.9%, and yet preferably 1.0%.

Meanwhile, in order to more easily attain the effect, the upper limit ofthe content is more preferably 4%, still more preferably 3.5%, and mostpreferably 3%.

In order to include the BaO component, Ba(NO₃)₂, BaSO₄, and the like canbe used as the glass material.

In order to attain a high clarification effect while maintaining lowexpansion characteristics, it is possible to contain, in addition to theBaO component, the ZnO component. The ZnO component is a component whichmay be easily the constitutive elements of β-quartz solid solution. Whencombined with a predetermined amount of a SiO₂ component and a P₂O₅component, the ZnO component is effective for improving thelow-expansion property of the crystallized glass and for reducing thedeformation thereof at high temperature. Also, the ZnO component iseffective for significantly improving meltability and clarity of theglass material and may be optionally contained in the present invention.

In the case of containing the ZnO component, when the content of the ZnOcomponent is 5.5% or less, low expansion characteristics are remarkablyimproved, thus making it possible to easily obtain ultra-low expansioncharacteristics. In addition, devitrification resistance of the glassmaterial is more improved and coarsening of the precipitated crystal inthe glass ceramics after the crystallization stage due to deteriorationof the devitrification resistance is suppressed, thus mechanicalstrength is increased.

In order to more easily attain the effect, the lower limit of thecontent is preferably 0.1%, more preferably 0.2%, still more preferably0.3%, and most preferably 0.4%.

Meanwhile, in order to more easily attain the effect, the upper limit ofthe content is more preferably 4%, still more preferably 3%, and mostpreferably 2.6%.

In order to include the ZnO component, ZnO, ZnSO₄, and the like can beused as the glass material.

In order to improve meltability and defoaming property of the glass, inthe present invention, the total content of the BaO component and theZnO component (on an oxide basis) is preferably 1% or more, morepreferably 1.5% or more, and still more preferably 2.0% or more. Thereason is that this total content causes a decrease in viscosity of theglass, thus making it easy to melt the glass and to cause defoaming.Also, the total content is controlled within the above range so as toattain a high clarification effect in the present invention.

Meanwhile, excess total content of the BaO component and the ZnOcomponent may cause deterioration of devitrification resistance anddeterioration of low expansion property. Therefore, the total content ofthe BaO component and the ZnO component (on an oxide basis) in thepresent invention is preferably 5.5% or less, more preferably 5% orless, and still more preferably 4% or less.

The SiO₂ component is a component associated with the case whereR-quartz and/or β-quartz solid solution is/are precipitated as the maincrystal phase by a heat treatment of the glass material. In the presentinvention, the content of the SiO₂ component is 30% or more and 70% orless.

When the content of the SiO₂ component is 30% or more, the precipitatedcrystal of the obtained crystallized glass is stabilized and itsstructure is less likely to be coarsened, thus improving the mechanicalstrength, leading to a decrease in surface roughness after polishing. Inorder to more easily obtain the effect, the lower limit of the contentis more preferably 45%, still more preferably 51%, and most preferably53%.

Meanwhile, when the content of the SiO₂ component is 70% or less,meltability and shapability of the glass material is enhanced and alsohomogeneousness is improved. In order to more easily attain the effect,the upper limit of the content is preferably 65%, more preferably 60%,and most preferably 58%.

In order to include the SiO₂ component, SiO₂, ZrSiO₄, and the like canbe used as the glass material.

When the amount of the Al₂O₃ component is 10% or more, the glassmaterial is easily melted, thus improving homogeneousness of theobtained crystallized glass and chemical durability of the crystallizedglass. In order to more easily attain the effect, the lower limit of thecontent is more preferably 20%, and most preferably 22%.

Meanwhile, when the amount of the Al₂O₃ component is 40% or less,devitrification resistance of the glass material is improved and thestructure of the crystallized glass is prevented from being coarsenedduring the crystallization stage due to deterioration of thedevitrification resistance, leading to an increase in mechanicalstrength. In order to more easily attain the effect, the upper limit ofthe content is preferably 30%, more preferably 27%, and most preferably26%.

In order to include the Al₂O₃ component, Al₂O₃, Al(PO₃)₃, Al(OH)₃, andthe like can be used as the glass material.

The P₂O₅ component has the effect of improving the meltability andclarity of the glass material, and the effect of stabilizing the thermalexpansion after the heat treatment for crystallization to be a desiredvalue. The effect may be more enhanced by combining with the SiO₂component. In the crystallized glass of the present invention, when theamount of the P₂O₅ component is 5% or more, the above effect isremarkably improved. In order to more easily attain the effect, thelower limit of the content is preferably 5%, more preferably 5.5%, andmost preferably 6%.

Meanwhile, when the amount of the P₂O₅ component is 15% or less,devitrification resistance of the glass material is improved and thestructure of the glass ceramics is prevented from being coarsened duringthe crystallization stage due to deterioration of the devitrificationresistance, leading to an increase in mechanical strength. In order tomore easily attain the effect, the upper limit of the content is morepreferably 13%, still more preferably 10%, and most preferably 9%.

In order to include the P₂O₅ component, Al(PO₃)₃, Ba(PO₃)₂, and the likecan be used as the glass material.

The total content of the SiO₂ component, the Al₂O₃ component, and theP₂O₅ component is preferably 65 to 93% (SiO₂+Al₂O₃+P₂O₅=65 to 93%). Aratio of the content of the P₂O₅ component to that of the SiO₂ component(P₂O₅)/SiO₂) is preferably 0.02 to 0.200. A ratio of the content of theP₂O₅ component to that of the Al₂O₃ component (P₂O₅/Al₂O₃) is preferably0.059 to 0.448. If any one of these conditions is satisfied, or two ormore conditions are satisfied, it becomes easy to significantly improvelow expansion characteristics at temperature range of 0 to 50° C., thusmaking it possible to easily obtain ultra-low expansion characteristics.

In order to more easily attain the effect, the lower limit of the totalcontent of SiO₂, Al₂O₃, and P₂O₅ is more preferably 75%, still morepreferably 80%, and most preferably 82%. Meanwhile, in order to moreeasily attain the effect, the upper limit of the total content of SiO₂,Al₂O₃, and P₂O₅ is more preferably 91%, and most preferably 89%.

In order to more easily attain the effect, the lower limit of P₂O₅/SiO₂is more preferably 0.08, and most preferably 0.12. Meanwhile, in orderto more easily obtain the effect, the upper limit of OP 0/SiO₂ is morepreferably 0.18, still more preferably 0.16, and most preferably 0.14.

In order to more easily attain the effect, the lower limit of P₂O₅/Al₂O₃is more preferably 0.150, still more preferably 0.210, and mostpreferably 0.250. Meanwhile, in order to more easily attain the effect,the upper limit of P₂O₅/Al₂O₃ is more preferably 0.400, still morepreferably 0.380, and most preferably 0.350.

The Li₂O or MgO component is a component which may be easily theconstitutive elements of β-quartz solid solution.

When combined with a SiO₂ component and a P₂O₅ component in the abovecomposition range, the Li₂O or MgO component is effective for improvingthe low-expansion property of the crystallized glass and for reducingthe deformation thereof at high temperature. Also, the Li₂O or MgOcomponent is effective for significantly improving meltability andclarity of the glass material. The glass can optionally contain each ofthese components in the case of expecting to easily obtain the effect,and it is particularly preferred to contain 0% or more (excluding 0%) ofthe Li₂O component.

It is more preferred that the amount of the Li₂O component is 1% or moresince the effect is remarkably improved and also meltability of theglass material is improved, whereby, homogeneousness is improved andalso precipitation of β-quartz or β-quartz solid solution is remarkablyimproved. In order to more easily attain the effect, the lower limit ofthe content is more preferably 2%, and most preferably 3%.

Meanwhile, when the content of the Li₂O component is 10% or less,ultra-low expansion characteristic can be easily obtained by remarkablyimproving low expansion characteristics. Also, devitrificationresistance of the glass material is more improved, whereby, coarseningof the precipitated crystal in the crystallized glass after thecrystallization stage due to deterioration of the devitrificationresistance is suppressed, thus increasing mechanical strength. In orderto make it easier to attain the effect, the upper limit of the contentis more preferably 8%, still more preferably 6%, yet preferably 5%, andmost preferably 4.6%.

In order to include the Li₂O component, Li₂CO₃, Li₂SO₄, and the like canbe used as the glass material.

The MgO component is a component which can be optionally added so as toattain the effect. When the amount of the MgO component to be added is0.1% or more, the effect is remarkably improved. In order to more easilyattain the effect, the lower limit of the content is more preferably0.4%, still more preferably 0.5%, and most preferably 0.7%.

Meanwhile, when the content of the MgO component is 5% or less, lowexpansion characteristics are remarkably improved, thus making itpossible to obtain ultra-low expansion characteristics. In order to moreeasily attain the effect, the upper limit of the content is morepreferably 3%, and most preferably 2%.

In order to contain the MgO component, MgO, MgSO₄, and the like can beused as the glass material.

The CaO component basically remains in the glass matrix other than thecrystals precipitated in the glass, thereby exerting some influences onthe effect of improving the ultra-low-expansion characteristics and themeltability of the glass, and capable of being optionally contained asthe component for delicate control of the relative amount of the crystalphase to the glass matrix phase. It is also possible to attain the meltclarification effect by containing more than 0% of the CaO component,and melt clarification effect can be remarkably attained when the amountis 0.3% or more. In order to more easily attain the effect, the lowerlimit of the content of the CaO component is most preferably 0.5%.

Meanwhile, when the content of the CaO component is 5% or less, lowexpansion characteristics are remarkably improved, thus easily attainingultra-low expansion characteristics. Also, devitrification resistance ofthe glass material is more improved, whereby, coarsening of theprecipitated crystal in the crystallized glass after the crystallizationstage due to deterioration of the devitrification resistance issuppressed, thus increasing mechanical strength. In order to more easilyattain the effect, the upper limit of the content of the CaO componentis more preferably 3%.

In order to include the CaO component, CaCO₃, CaSO₄, and the like can beused as the glass material.

The TiO₂ component and the ZrO₂ component are both components useful asa crystal nucleating agent. In the present invention, when 1% or moreand 10% or less of at least either one of the TiO₂ component or the ZrO₂component is contained, the objective crystal phase is easilyprecipitated and also no unmolten substance is generated, which leads tosatisfactory meltability of the glass material and an improvement inhomogeneousness.

In order to more easily attain the effect (to enable precipitation ofthe objective crystal phase), the lower limit of the content of TiO₂ ispreferably 1%, more preferably 1.3%, and most preferably 1.5%. The lowerlimit of the content of ZrO₂ is preferably 1%, more preferably 1.2%, andmost preferably 1.5%. The lower limit of the total content of the TiO₂component and the ZrO₂ component is preferably 1%, more preferably 1.5%,still more preferably 2.0%, and most preferably 2.5%.

Meanwhile, in order to more easily attain the effect (no unmoltensubstance is generated, which leads to satisfactory meltability of theglass material and an improvement in homogeneousness), the upper limitof the content of TiO₂ is preferably 10%, more preferably 7%, still morepreferably 5%, and most preferably 4%. For the same reason, the upperlimit of the content of ZrO₂ is preferably 10%, more preferably 7%,still more preferably 5%, and most preferably 4%. The total upper limitof the content of the TiO₂ component and the ZrO₂ component ispreferably 10%, more preferably 7%, still more preferably 5%, and mostpreferably 4%.

In order to contain the TiO₂ component, TiO₂, and the like can be usedas the glass material.

In order to contain the ZrO₂ component, ZrO₂, ZrSiO₄, and the like canbe used as the glass material.

The As₂O₃ component is a component capable of becoming environmentallyharmful, and it should not be substantially included. Since thecrystallized glass of the present invention is capable of attaining theclarification effect without including the As₂O₃ component, it ispreferred that the crystallized glass does not substantially contain theAs₂O₃ component so as to reduce an adverse influence on the environment.

The Sb₂O₃ is also a component capable of becoming environmentallyharmful, and its use must be reduced as much as possible. Since thecrystallized glass of the present invention is capable of attaining theclarification effect without containing the Sb₂O₃ component, it ispreferred that the crystallized glass does not substantially contain theSb₂O₃ component so as to reduce an adverse influence on the environment.

In addition to the above-mentioned components, the crystallized glass ofthe present invention may further contain one, or two or more of othercomponents such as SrO, B₂O₃, F₂, La₂O₃, Bi₂O₃, WO₃, Y₂O₃, and Gd₂O₃ inthe total amount of 5% or less, and may also contain one, or two or moreof coloring components such as CoO, NiO, MnO₂, Fe₂O₃, and Cr₂O₃ in thetotal amount of 5% or less, for the purpose of delicate control of thecharacteristics of the glass without impairing the characteristicsthereof. However, when the crystallized glass of the present inventionis used for applications which require high light transmittance, it ispreferred that the crystallized glass does not contain theabove-mentioned coloring components.

In the present invention, it is possible to further contain the fluoridecomponent and the sulfate component, optionally, in expectation of theadditional clarification effect. In the melting process of the glass, adecomposition gas is generated from the fluoride component and thesulfate component and the decomposition gas is combined with othergasses (bubbles) in the molten glass to form large bubbles which arelikely to float on the surface, thus improving the property of removingthe bubbles in the molten glass.

For example, MgF₂ and CaF₂ can be added as the fluoride component, andBaSO₄, Li₂SO₄, and ZnSO₄ can be added as the sulfate component. In orderto attain the clarification effect due to these components, the lowerlimit of the total additive amount of the fluoride component as F₂ andthe sulfate component as SO₃ is preferably 0.03 part by weight, and morepreferably 0.05 part by weight, relative to 100 parts by weight of thecomposition other than these components on an oxide basis. Meanwhile,the upper limit of the total additive amount of these components issufficiently 2 parts by weight, more preferably 1 part by weight, andmost preferably 0.1 part by weight.

In order to attain the clarification effect due to these components, thelower limit of each additive amount of these components is preferably0.03 part by weight, and more preferably 0.05 part by weight. Meanwhile,in order to attain the effect, the upper limit of each additive amountof the above components is preferably 2 parts by weight, more preferably1 part by weight, and most preferably 0.1 part by weight.

In the present invention, it is possible to further contain one, or twoor more of a MnO₂ component, a WO₃ component, a Ta₂O₃ component, and anNb₂O₅ component, optionally, in expectation of the additionalclarification effect.

In order to attain the clarification effect, the lower limit of thetotal content of the MnO₂ component, the WO₃ component, the Ta₂O₅component, and the Nb₂O₅ component is more preferably 0.05%, and mostpreferably 0.2%. Meanwhile, the upper limit of the total content ofthese components is sufficiently 5%, more preferably 3%, and mostpreferably 1.5%.

In order to attain the clarification effect, the lower limit of thecontent of these components is more preferably 0.05%, and mostpreferably 0.2%. Meanwhile, in order to attain the effect, the upperlimit of each content of these components is preferably 5%, morepreferably 2%, and most preferably 1.5%.

In the present invention, it is preferred that the glass contain neithera CeO₂ component nor a SnO₂ component. When the glass contains the CeO₂component, defoaming may not be sufficiently performed and thecrystallized glass may undergo coloration in the production of thecrystallized glass. When the glass contains SnO₂, the crystallized glassmay undergo devitrification and the crystallized glass may undergocoloration, and also deterioration of members used in the productionprocess may proceed.

Particularly, when the crystallized glass is intended to obtainultra-low expansion characteristics, a main crystal phase having anegative average linear thermal expansion coefficient is precipitated inthe glass, and combined with the glass matrix phase having a positiveaverage linear thermal expansion coefficient, thereby realizingultra-low expansion characteristics as a whole. For this, it ispreferred that the glass does not contain a crystal phase having apositive average linear thermal expansion coefficient, that is, lithiumdisilicate, lithium silicate, α-quartz, α-cristobalite, α-tridymite,petalite including Zn-petalite, wollastonite, forsterite, diopsite,nepheline, clinoenstatite, anorthite, celsian, gehlenite, feldspar,willemite, mullite, corundum, rankinite, larnite, and solid solutionsthereof. In addition to these, it is also preferred that the glass doesnot contain tungstates such as Hf tungstate and Zr tungstate, titanatessuch as magnesium titanate, barium titanate and manganese titanate, andmullite, 2-barium 3-silicate, Al₂O₃.5SiO₂, and solid solutions thereof,so as to maintain satisfactory mechanical strength thereof.

Next, the crystallized glass of the present invention is produced by thefollowing method. First, glass materials are weighed, formulated, putinto a crucible or the like, and then melted at about 1,450 to 1,600° C.to obtain a glass material.

The glass material is preferably mixed with a clarifying agent fordefoaming of the glass. The fluoride component, the sulfate component,and the chloride component can be used as the defoaming agent. It isparticularly preferred to mix one or more defoaming agents selected fromBaSO₄, Li₂SO₄ and ZnSO₄. Mixing of the raw material with one or moreclarifying agents selected from BaSO₄, Li₂SO₄, and ZnSO₄ enablesattainment of high defoaming effect without using the clarifying agent,which has often been used heretofore, such as As₂O₃ and Sb₂O₃, and alsoattainment of desired ultra-low expansion characteristics in thecrystallized glass.

When the amount of BaSO₄ to be mixed in the raw material is 0.02% bymass or more based on the mass of the whole glass material containingBaSO₄, the defoaming effect can be attained. Therefore, the lower limitof the amount of BaSO₄ to be mixed in the raw material is preferably0.02% by mass, more preferably 0.03% by mass, and most preferably 0.035%by mass.

Meanwhile, when the amount of BaSO₄ to be mixed in the raw material ismore than 2% by mass based on the mass of the whole glass materialcontaining BaSO₄, excessive foaming occurs and bubbles are likely toremain in the melt of the glass material, thus making it impossible toattain the desired defoaming effect. Therefore, the upper limit of theamount of BaSO₄ to be mixed in the raw material is preferably 2% bymass, more preferably 1.9% by mass, and most preferably 1.8% by mass.

When the amount of Li₂SO₄ to be mixed in the raw material is 0.1% bymass or more based on the mass of the whole glass material containingLi₂SO₄, the defoaming effect can be attained. Therefore, the lower limitof the amount of Li₂SO₄ to be mixed in the raw material is preferably0.15% by mass, more preferably 0.2% by mass, and most preferably 0.3% bymass.

Meanwhile, the amount of Li₂SO₄ to be mixed in the raw material is morethan 2% by mass based on the mass of the whole glass material containingLi₂SO₄, excessive foaming occurs and bubbles are likely to remain in themelt of the glass material, thus making it impossible to attain thedesired defoaming effect. Therefore, the upper limit of the amount ofLi₂SO₄ to be mixed in the raw material is preferably 1.9% by mass, morepreferably 1.8% by mass, and most preferably 1.7% by mass.

When the amount of ZnSO₄ to be mixed in the raw material is 0.05% bymass or more based on the mass of the whole glass material containingZnSO₄, the defoaming effect can be attained. Therefore, the lower limitof the amount of ZnSO₄ to be mixed in the raw material is preferably0.06% by mass, more preferably 0.07% by mass, and most preferably 0.08%by mass.

Meanwhile, the amount of ZnSO₄ to be mixed in the raw material is morethan 1.5% by mass based on the mass of the whole glass materialcontaining ZnSO₄, excessive foaming occurs and bubbles are likely toremain in the melt of the glass material, thus making it impossible toattain the desired defoaming effect. Therefore, the upper limit of theamount of ZnSO₄ to be mixed in the raw material is preferably 1.0% bymass, more preferably 0.8% by mass, and most preferably 0.7% by mass.

The lower limit of the total amount of one or more defoaming agentsselected from BaSO₄, Li₂SO₄, and ZnSO₄ to be mixed in the raw materialis preferably 0.02% by mass, more preferably 0.03% by mass, and mostpreferably 0.035% by mass, based on the mass of the whole glass materialfrom the viewpoint of attaining the defoaming effect.

Meanwhile, the upper limit of the total amount of one or more defoamingagents selected from BaSO₄, Li₂SO₄, and ZnSO₄ to be mixed in the rawmaterial is preferably 2% by mass, more preferably 1.9% by mass, andmost preferably 1.8% by mass, based on the mass of the whole glassmaterial from the viewpoint of suppressing excessive foaming to attainthe desired defoaming effect.

As mentioned above, the glass material is melted, cast into a moldand/or hot-shaped into a desired form, and then slowly cooled.

Next, the glass material is subjected to a heat treatment for convertinginto a crystallized glass. First, it is maintained at a temperature of650 to 750° C., thereby promoting formation of crystal nuclei. Thetemperature of the heat treatment is more preferably controlled to 680°C. as the lower limit, and the heat treatment is more preferablycontrolled to 720° C. as the upper limit. After forming crystal nuclei,crystallization is conducted at a temperature of 750 to 850° C. When thetemperature is lower than 750° C., the main crystal phase could notfully grow and, when it is higher than 850° C., it is undesirable sincethe glass material is likely to cause softening and deforming orre-melting.

Further, a mask, an optical reflection mirror, a wafer stage, areticular stage, and a precision member can be obtained by forming theobtained glass ceramics into desired forms, followed by optional formingsuch as lapping, polishing, and film formation thereon.

Next, preferred Examples of the present invention will be describedbelow.

In Tables 1 to 6, each glass composition and number of bubbles remainingper 1 cm³ of the glass after melting of Examples 1 to 16, andComparative Examples 1 and 2 are shown. In Tables 7 to 11, eachcomposition of the glass materials of Example 1 to 16 is shown. Thecomposition of the glass material represents % by mass of each rawmaterial relative to 100% by mass of the whole glass material. InComparative Example 1, the arsenic component is contained so as to exertthe clarification effect. In Comparative Examples, none of BaSO₄,Li₂SO₄, and ZnSO₄ is mixed in the glass material. Bubbles as used hereinare bubbles having a diameter (φ) of 10 μm or more. Light transmittancewavelength at a thickness of 10 mm (values at 5% and 80%) is shown inTables 1, 2, 5, and 6, and an average linear thermal expansioncoefficient (α) at 0 to 50° C. is shown in Tables 1 to 6. Eachcomposition of the respective Examples and Comparative Examples wereexpressed by % by mass. The present invention is not limited only to thefollowing Examples.

According to the formulation of raw materials shown in Tables 7 to 11,raw materials of oxide, carbonate, sulfide, and nitrate were mixed andmelted using a common melting device at a temperature of about 1,450 to1,600° C. After stirring for homogenization, the resulting melt mixturewas shaped and cooled to obtain a glass material (amorphous glass). Theglass material was then subjected to a heat treatment at 650 to 750° C.for about 1 to 150 hours to form crystal nuclei, which was crystallizedby subjecting to a heat treatment at 750 to 850° C. for about 1 to 300hours to obtain a crystallized glass.

The number of bubbles remaining is an average of the number of bubblesat five positions in the case of counting the number of bubblesincluding a thickness direction with respect to optional five positions(plane measuring 1 cm²×5) of a square surface of the glass material(square measuring 100 mm on a side, and 10 mm in thickness) using astereoscopic microscope (SZ60, manufactured by OLYMPUS CORPORATION).

A crystallized glass made from the glass material after the measurementof the number of bubbles remaining, and an average linear thermalexpansion coefficient (α) at 0 to 50° C. with respect to thecrystallized glass was measured.

The average linear thermal expansion coefficient was measured using aFizeau interferometry-type accurate expansion coefficient measuringapparatus. The measuring sample has a cylindrical shape having adiameter of 6 mm and a length of about 80 mm. An optical flat plate isbrought into contact with both ends of a measuring sample, therebyenabling observation of interference fringes by a He—Ne laser, and thenthe sample is put in a temperature controllable furnace. Next, thetemperature of the measuring sample is changed and a change ininterference fringes is observed to measure a change in length of themeasuring sample depending on the temperature. In the present invention,after temperature rising or falling at 0.5° C./min in the temperaturerange of 0 to 50° C., an amount of a change in measuring sample lengthwas plotted every 5 seconds and a quintic approximation curve was drawn,and then an average linear thermal expansion coefficient from 0 to 50°C., and (maximum value−minimum value) of ΔL/L in the temperature rangeof 0 to 50° C. were measured. Both the average linear thermal expansioncoefficient and the (maximum value−minimum value) of the ΔL/L−temperature curve are averages during temperature rising and falling.

With respect to the obtained glass material and crystallized glass, arefractive index (nd) and an Abbe number (νd) were measured according toJapan Optical Glass Industrial Standard JOGIS 2003-01, and a lighttransmittance (wavelength for 80% light transmittance λ₈₀ and wavelengthfor 5% light transmittance λ₅) was measured according to JOGIS 2003-02,and then a specific gravity was measured according to JOGIS 1975-05.

As shown in Tables 1 to 5, in the crystallized glasses of Examples,regarding high expansion characteristics, an average linear thermalexpansion coefficient at 0 to 50° C. was within 0.0±1.0 (10⁻⁶/° C.).Especially in Examples 1 to 4 and 17 to 20, since the number of bubblesremaining in 1 cm³ of the crystallized glass is less than 2, and also anaverage linear thermal expansion coefficient (α) is within 0.0±0.5(10⁻⁷/° C.) in the temperature range of 0 to 50° C., they exhibitclarity and ultra-low expansion characteristics corresponding to theresults when using the arsenic component in Comparative Example 1 shownin Table 6.

Like Comparative Example 2 shown in Table 6, when the total content ofthe BaO component and the ZnO component (on an oxide basis) is less than1%, the number of bubbles remaining in 1 cm³ of the glass is 33, andthus it is considered that the glass has no clarity.

TABLE 1 Examples Sample 1 2 3 4 Composition SiO₂ 55.500 55.500 55.50055.500 [% by mass] Al₂O₃ 24.500 24.500 24.500 24.500 P₂O₅ 7.500 7.5007.500 7.500 Li₂O 3.800 3.800 3.800 3.800 MgO 1.000 1.000 1.000 1.000 CaO1.050 1.050 1.050 1.050 BaO 1.100 1.200 1.500 1.470 ZnO 1.250 1.1500.850 0.880 ZrO₂ 2.000 2.000 2.000 2.000 TiO₂ 2.300 2.300 2.300 2.300As₂O₃ — — — Total 100.000 100.000 100.000 100.000 BaO + ZnO 2.35 2.352.35 2.35 SiO₂ + Al₂O₃ + P₂O₅ 87.500 87.500 87.500 87.500 P₂O₅/SiO₂0.135 0.135 0.135 0.135 P₂O₅/Al₂O₃ 0.306 0.306 0.306 0.306 TiO₂ + ZrO₂4.300 4.300 4.300 4.300 Number of bubbles remaining 0.8 0.2 0.4 0.4(bubbles/cm³) Amorphous nd 1.52882 1.52868 1.52827 1.52852 glass νd 57.458.6 58.6 57.7 Wavelength for 80% 373 374 372 372 transmittance (nm)Wavelength for 5% 326 325 325 325 transmittance (nm) Specific gravity2.47 2.47 2.47 2.47 Crystallized nd 1.54373 1.54329 1.54237 1.54238glass νd 55.8 56.1 56.1 56.0 Wavelength for 80% 482 480 484 488transmittance (nm) Wavelength for 5% 379 378 380 379 transmittance (nm)Specific gravity 2.54 2.54 2.53 2.53 α(0° C. to 50° C.) −0.50 −0.32 0.500.44 (×10⁻⁷/° C.)

TABLE 2 Examples Sample 5 6 7 8 Composition SiO₂ 55.800 55.900 56.40055.900 [% by mass] Al₂O₃ 24.600 24.700 24.700 24.700 P₂O₅ 7.500 7.6007.600 7.600 Li₂O 3.800 3.900 3.800 4.000 MgO 1.000 1.000 0.900 1.000 CaO1.100 0.800 0.500 1.000 BaO 1.400 1.050 1.150 0.950 ZnO 0.500 0.8500.950 0.550 ZrO₂ 2.000 2.000 2.000 2.000 TiO₂ 2.300 2.200 2.000 2.300As₂O₃ — — — Total 100.000 100.000 100.000 100.000 BaO + ZnO 1.90 1.902.10 1.50 SiO₂ + Al₂O₃ + P₂O₅ 87.900 88.200 88.700 88.200 P₂O₅/SiO₂0.134 0.136 0.135 0.136 P₂O₅/Al₂O₃ 0.305 0.308 0.308 0.308 TiO₂ + ZrO₂4.300 4.200 4.000 4.300 Number of bubbles remaining 1.5 1.5 0.2 2.0(bubbles/cm³) Amorphous nd 1.52755 1.52697 1.52476 1.52748 glass νd 58.057.8 57.7 57.7 Wavelength for 80% 378 379 377 381 transmittance (nm)Wavelength for 5% 327 327 325 329 transmittance (nm) Specific gravity2.46 2.46 2.45 2.46 Crystallized nd 1.54196 1.54251 1.53908 1.54298glass νd 55.9 55.8 56.9 55.8 Wavelength for 80% 488 482 610 473transmittance (nm) Wavelength for 5% 380 379 379 380 transmittance (nm)Specific gravity 2.53 2.53 2.52 2.53 α(0° C. to 50° C.) 0.90 −0.90 −2.00−0.42 (×10⁻⁷/° C.)

TABLE 3 Examples Sample 9 10 11 12 Composition SiO₂ 50.500 54.500 56.40055.560 [% by mass] Al₂O₃ 26.250 26.000 23.600 26.250 P₂O₅ 6.050 8.1008.000 6.080 Li₂O 3.550 3.400 3.300 3.950 MgO 5.000 1.400 0.720 1.400 CaO0.050 1.500 0.620 1.620 BaO 2.550 1.200 3.050 1.520 ZnO 2.550 0.4000.620 1.000 ZrO₂ 2.000 1.300 2.250 1.000 TiO₂ 1.500 2.200 1.440 1.620Total 100.000 100.000 100.000 100.000 BaO + ZnO 5.10 1.60 3.67 2.52SiO₂ + Al₂O₃ + 82.800 88.600 88.000 87.890 P₂O₅ P₂O₅/SiO₂ 0.120 0.1490.142 0.109 P₂O₅/Al₂O₃ 0.230 0.312 0.339 0.232 TiO₂ + ZrO₂ 3.500 3.5003.690 2.620 Number of bubbles remaining 1.2 1.4 1.8 1.4 (bubbles/cm³)α(0° C. to 50° C.) 7.6 7.5 1.7 1.05 (×10⁻⁷/° C.)

TABLE 4 Examples Sample 13 14 15 16 Composition SiO₂ 56.000 58.60059.600 50.800 [% by mass] Al₂O₃ 25.000 22.200 23.230 23.950 P₂O₅ 6.0005.050 5.050 9.050 Li₂O 4.500 3.030 4.550 3.700 MgO 1.000 1.010 1.2001.800 CaO 0.500 0.510 0.800 2.550 BaO 1.000 3.030 1.200 2.550 ZnO 1.0002.020 0.800 1.000 ZrO₂ 1.500 2.020 1.520 3.500 TiO₂ 3.500 2.530 2.0501.100 Total 100.000 100.000 100.000 100.000 BaO + ZnO 2.00 5.05 2.003.55 SiO₂ + Al₂O₃ + 87.000 85.850 87.880 83.800 P₂O₅ P₂O₅/SiO₂ 0.1070.086 0.085 0.178 P₂O₅/Al₂O₃ 0.240 0.227 0.217 0.378 TiO₂ + ZrO₂ 5.0004.550 3.570 4.600 Number of bubbles remaining 1.4 2.0 2.4 1.2(bubbles/cm³) α(0° C. to 50° C.) −1.28 0.66 −2.4 8.4 (×10⁻⁷/° C.)

TABLE 5 Examples Sample 17 18 19 20 Composition SiO₂ 55.500 55.50055.500 55.500 [% by mass] Al₂O₃ 24.500 24.500 24.500 24.500 P₂O₅ 7.5007.500 7.500 7.500 Li₂O 3.800 3.800 3.800 3.800 MgO 1.000 1.000 1.0001.000 CaO 1.050 1.050 1.050 1.050 BaO 1.100 1.100 1.100 1.100 ZnO 1.2501.250 1.250 1.250 ZrO₂ 2.000 2.000 2.000 2.000 TiO₂ 2.300 2.300 2.3002.300 As₂O₃ — — — Total 100.000 100.000 100.000 100.000 BaO + ZnO 2.3502.350 2.350 2.350 SiO₂ + Al₂O₃ + P₂O₅ 87.500 87.500 87.500 87.500P₂O₅/SiO₂ 0.135 0.135 0.135 0.135 P₂O₅/Al₂O₃ 0.306 0.306 0.306 0.306TiO₂ + ZrO₂ 4.300 4.300 4.300 4.300 Number of bubbles remaining 0.5 0.90.6 0.8 (bubbles/cm³) Amorphous nd 1.52872 1.52881 1.52879 1.52885 glassνd 57.4 57.4 57.4 57.4 Wavelength for 80% 372 373 374 373 transmittance(nm) Wavelength for 5% 325 326 325 326 transmittance (nm) Specificgravity 2.47 2.47 2.47 2.47 Crystallized nd 1.54373 1.5437 1.543691.54375 glass νd 55.8 55.8 55.7 55.8 Wavelength for 80% 482 480 481 480transmittance (nm) Wavelength for 5% 379 378 378 379 transmittance (nm)Specific gravity 2.54 2.54 2.54 2.54 α(0° C. to 50° C.) −0.31 −0.45−0.35 −0.5 (×10⁻⁷/° C.)

TABLE 6 Comparative Examples Sample 1 2 Composition SiO₂ 55.500 60.380[% by mass] Al₂O₂ 24.500 23.570 P₂O₅ 7.500 5.420 Li₂O 3.800 2.810 MgO1.000 1.810 CaO 1.050 0.000 BaO 0.765 0.000 ZnO 1.085 0.990 ZrO₂ 2.0002.510 TiO₂ 2.300 2.510 As₂O₃ 0.500 0.000 Total 100.000 100.000 BaO + ZnO1.850 0.990 SiO₂ + Al₂O₃ + P₂O₅ 87.500 89.370 P₂O₅/SiO₂ 0.135 0.090P₂O₅/Al₂O₃ 0.306 0.230 TiO₂ + ZrO₂ 4.300 5.020 Number of bubblesremaining 0 33 (bubbles/cm³) Amorphous nd 1.52760 — glass νd 57.8 —Wavelength for 80% 373 — transmittance (nm) Wavelength for 5% 328 —transmittance (nm) Specific gravity 2.46 — Crystallized nd 1.54454 —glass νd 56.0 — Wavelength for 80% 442 — transmittance (nm) Wavelengthfor 5% 380 — transmittance (nm) Specific gravity 2.54 — α(0° C. to 50°C.) −0.02 8.10 (×10⁻⁷/° C.)

TABLE 7 Raw material Examples (% by mass) 1 2 3 4 SiO₂ 51.779 51.74551.648 51.653 Al₂O₃ 21.182 21.168 21.129 21.131 Al(PO₃)₃ 8.672 8.6678.650 8.651 Li₂CO₃ 8.767 8.761 8.744 8.745 MgO 0.933 0.932 0.931 0.931CaCO₃ 1.748 1.747 1.744 1.744 Ba(NO₃)₂ 1.670 1.828 2.221 2.253 BaSO₄0.071 0.071 0.141 0.071 ZnO 1.166 1.072 0.791 0.819 ZrO₂ 1.866 1.8651.861 1.861 TiO₂ 2.146 2.144 2.140 2.141 Total 100 100 100 100

TABLE 8 Raw material Examples (% by mass) 5 6 7 8 SiO₂ 51.937 52.19052.812 52.078 Al₂O₃ 21.225 21.363 21.426 21.316 Al(PO₃)₃ 8.652 8.7958.821 8.775 Li₂CO₃ 8.746 9.004 8.799 9.215 MgO 0.931 0.934 0.843 0.932CaCO₃ 1.827 1.333 0.836 1.663 Ba(NO₃)₂ 2.173 1.623 1.756 1.461 BaSO₄0.042 0.043 0.071 0.042 ZnO 0.465 0.794 0.890 0.512 ZrO₂ 1.861 1.8671.873 1.863 TiO₂ 2.141 2.054 1.873 2.143 Total 100 100 100 100

TABLE 9 Raw material Examples (% by mass) 9 10 11 12 SiO₂ 47.251 51.02552.472 51.415 Al₂O₃ 23.205 22.527 20.174 22.943 Al(PO₃)₃ 7.016 9.3999.225 6.973 Li₂CO₃ 8.213 7.872 7.592 9.038 MgO 4.678 1.311 0.670 1.295CaCO₃ 0.083 2.506 1.029 2.675 Ba(NO₃)₂ 2.472 4.757 1.609 BaSO₄ 1.4221.708 0.071 0.703 ZnO 2.386 0.375 0.577 0.925 ZrO₂ 1.871 1.217 2.0930.925 TiO₂ 1.403 2.060 1.340 1.499 Total 100 100 100 100

TABLE 10 Raw material Examples (% by mass) 13 14 15 16 SiO₂ 52.01054.834 55.208 46.543 Al₂O₃ 21.885 19.642 20.399 19.968 Al(PO₃)₃ 6.9075.857 5.798 10.277 Li₂CO₃ 10.335 7.011 10.422 8.383 MgO 0.929 0.9451.112 1.649 CaCO₃ 0.829 0.852 1.323 4.170 Ba(NO₃)₂ 1.108 3.716 3.123BaSO₄ 0.424 0.996 1.690 0.766 ZnO 0.929 1.890 0.741 0.916 ZrO₂ 1.3931.890 1.408 3.207 TiO₂ 3.251 2.367 1.899 1.008 Total 100 100 100 100

TABLE 11 Raw material Examples (% by mass) 17 18 19 20 SiO₂ 51.69751.394 51.710 51.497 Al₂O₃ 21.148 21.024 21.154 21.067 Al(PO₃)₃ 8.6598.608 8.661 8.626 Li₂CO₃ 8.638 7.786 8.755 8.719 Li₂SO₄ 0.199 1.5860.000 0.000 MgO 0.931 0.926 0.932 0.928 CaCO₃ 1.746 1.735 1.746 1.739Ba(NO₃)₂ 1.905 1.894 1.905 1.898 ZnO 1.071 1.065 1.048 0.881 ZnSO₄ 0.0000.000 0.082 0.656 ZrO₂ 1.863 1.852 1.863 1.856 TiO₂ 2.142 2.130 2.1432.134 Total 100.000 100.000 100.000 100.000

The crystallized glass of the present invention is expected to be used,as mirror substrate materials and photomask substrate materials, innext-generation semiconductor production devices utilizing extremeultraviolet lithography (EUVL), and is applicable to masks forlithography, optical reflection mirrors, parts of semiconductorproduction equipments such as wafer stages and reticle, parts ofliquid-crystal exposure devices, parts of large-size reflection mirrors,as well as to other various precision members such as parts of standardscales, prototypes and testers. Because of having high transparency, theglass ceramics of the present invention are usable in variousapplications which require high optical transmittance such as substratesfor optical filters, and transmission masks for lithography. Inaddition, the glass ceramics of the present invention are applicable toother various members because of having high mechanical strength, andthey may be effectively worked for weight reduction.

What is claimed is:
 1. A crystallized glass which contains none of anAs₂O₃ component, a Sb₂O₃ component, a SnO₂ component, and a CeO₂component (on an oxide basis) as a clarifying agent, comprising, interms of percent by mass on an oxide basis: an SiO₂ component includedat 30-70%, an Al₂O₃ component included at 10-40%, a Li₂O componentincluded at more than 0% and equal to or less than 10%, a P₂O₅ componentincluded at 5-15%, a TiO₂ component included at 1-10%, a ZnO componentincluded at 0-5.5%, and a BaO component included at more than 0% andequal to or less than 5%, wherein the total content of the BaO componentand the ZnO component (on an oxide basis) is 1.9% by mass or more. 2.The crystallized glass according to claim 1, containing β-quartz and/orβ-quartz solid solution as main crystal phase(s).
 3. The crystallizedglass according to claim 1, wherein the main crystal phase has anaverage crystal particle size of 5-200 nm.
 4. The crystallized glassaccording to claim 1, wherein an average linear thermal expansioncoefficient within a temperature range of 0-50° C. is within a range of0.0±1.0×10⁻⁶/° C.
 5. The crystallized glass according to claim 1,comprising, in terms of percent by mass on an oxide basis: a ZrO₂component included at 1-10%.
 6. The crystallized glass according toclaim 1, comprising, in terms of percent by mass on an oxide basis, anMgO component included at 0-5%, and a CaO component included at 0-5%.